NBSIR 74-588

Development of a Bench Test for

Type X Core Gypsum Board

J. L. Houser, Research Associate

Gypsum Association

Programmatic Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December 1974

Final Report

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 74-588

DEVELOPMENT OF A BENCH TEST FOR

TYPE X CORE GYPSUM BOARD

J. L. Houser, Research Associate

Gypsum Association

Programmatic Center for Fire Research

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December 1974

Final Report

U.S. DEPARTMEIMT OF COMMERCE, Frederick B. Dent. Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

CONTENTS

Page

1. INTRODUCTION 1

2. BACKGROUND 2

3. TEST APPARATUS 4

4. TEST SPECIMENS 9

5. TEST PROCEDURE 10

6. CALIBRATION OF APPARATUS 13

7. DISCUSSION OF RESULTS WITH PRESENT APPARATUS ... 14

8. DATA SECTION 18

8.1. Test Results of 1/2" Type X and Improved

Formula Type X 18

8.2. Test Results of 5/8" Type X and Improved

Formula Type X 19

8.3. Test Results of 1/2" and 5/8" Regular

Formula 20

9. CONCLUSIONS 21

10. RECOMMENDATIONS FOR FUTURE WORK 21

APPENDIX A. THERMAL VALUES OF GYPSUM 22

APPENDIX B. SI CONVERSION FACTORS 22

REFERENCES 23

iii

DEVELOPMENT OF A BENCH TEST

FOR TYPE X CORE GYPSUM BOARD

J. L. Houser^

This paper describes the development of a test

method for determining that the core material in a

gypsum board sample qualifies as Type X. A 2 inch

(5.08 cm) by 16 inch (40.64 cm) specimen is flexurally stressed during the test by suspending a weight from the cantilevered end of the test sample.

The specimen is swiveled into the center of a two

burner turbulent flame at an average temperature

of 1,780°F (971°C) . The burners are positioned

from above and below. The test is terminated when

the specimen either breaks or deflects through an

arc three times the specimen thickness. Results

show this method to be repeatable with a coefficient

of variation equal to + 8 percent for a given type

of material from a single manufacturer.

Key words: Building codes; construction materials;

fire endurance ratings; fire tests; gypsum.

1. INTRODUCTION

The gypsum industry currently produces gypsum board products at an annual rate in excess of 14 billion square feet

[1]^. These products constitute more than 80 percent of all

finished wall and ceiling surface materials used in the United

States construction industry. Approximately one-fifth of this

total production is devoted to special fire resistant products

that go into systems and assemblies which are required to have

a fire endurance rating as determined by the "Standard Method

of Fire Tests of Building Construction and Materials", ASTM

Designation E 119 [2]

These fire rated assemblies are used as wall systems for

occupancy separations and public exitways, chases, shafts,

column and beam fire protection and floor/ceiling systems.

They are used primarily in commercial, institutional and multifamily residential occupancies and high-rise construction. The

basic gypsum board product used in these rated assemblies has

a special core formulation that includes noncombustible fibers

and is defined generically as Type X by ASTM Standard C 36 [3]

^This work was conducted while Mr. Houser was a Research

Associate for the Gypsum Association at the National Bureau

of Standards. He is currently Assistant Merchandise Manager

for the Gypsum Products for the Flintkote Company.

^Figures in brackets indicate the literature references at the

end of this paper.

1
Gypsum has several unique properties which make it an

effective barrier to fire. Chemically expressed as CaSO^ • 2H2O

or technically as "dihydrous calcium sulphate", it is about

50 percent water by volume or about 21 percent water by weight.

When gypsum is exposed to a high temperature most of the chemically combined water of crystallization is slowly released as

steam, a process known as calcination. The temperature behind

the plane of calcination is just slightly higher than that of

boiling water. Even after calcination is complete the gypsum

remaining in place acts an an insulating barrier to the transmission of heat and flame.

In the early 1940 's, efforts were made to improve the fire

resistive characteristics of regular gypsum wallboard. Experimentation with additives to the core material led to the first

patent on a special fire retardant gypsum wallboard. This

patent was issued to Michael Croce and Clarence Shuttleworth

of the Certain-teed Products Corporation^ on October 11, 1950

(#2526066) based on work originally filed in 1943 [4]. The

first Underwriters' Laboratories (UL) materials listing of

special fire retardant gypsum wallboard appeared in 1946.

Further refinements of the original patent work resulted in

the use of unexpanded vermiculite and siliceous clays to stabilize the core thermally and compensate for the effect of

shrinkage during calcination. Glass fibers dispersed throughout the core act as a reinforcing mat to hold the calcined core

intact for extended periods of time during exposure to fire.

This report describes the development of a laboratory

test method that defines by performance whether mill production

material can qualify within known acceptable standards as Type

X core gypsum board. , .

2. BACKGROUND

The need to develop a reliable bench test to determine

Type X core gypsum board is demonstrated by the fact that ASTM

Committee C-11 on Ceilings and Walls has carried the subject

as an agenda item for several years. There are currently two

alternative bench test methods under study by C-11 for the

determination of Type X core.

One method described in ASTM C-473 [5] , suspends a 2 inch

(5.08 cm) by 12 inch (30.48 cm) specimen vertically between

two Meeker burner flames. The specimen has a 1,000 gram weight

attached to the lower edge and failure is recorded when the

specimen breaks.

Gypsum Division is now part of the Georgia-Pacific Corporation.

2
The second method uses 2 inch (5.08 cm) by 8 inch (20.32

cm) specimens that are first calcined in a muffle furnace at

800°F (427°C) for two hours. The sample is then placed over

a fulcrum and lead shot is added at a measured rate to a cup

supported at a cantilevered end. The weight of the shot is

measured when the specimen breaks as an indication of the

relative strength of the calcined core.

The merits of each of these test methods were considered

in the design of the method presented for discussion in this

paper. However, after careful visual observations of the

behavior of Type X gypsum wallboard during the course of 18

full-scale wall and floor/ceiling ASTM E-119 furnace tests,

it was concluded that the forces acting on the wallboard in

such severe fire exposures are flexural rather than tensile.

This was a paramount consideration in the selection of the

orientation for the specimen within the apparatus in this proposed method.

Other considerations were the form and degree of thermal

exposure. Following consultation with several experts in the

field of combustion, it was decided to produce a premixed turbulent flame impinging on the specimen with a temperature range

between 1,500 and 2,000"^. The average flame temperature would

then correspond to an exposure time on the standard timetemperature curve in excess of one hour and twenty minutes. In

order to achieve consistent results it was also important that

the flame area be concentrated in a sharply defined path across

the specimen instead of concentric radiations of varying flux.

The criteria set forth for the design of this test method

were as follows:

1. The test must relate to accepted large-scale tests in

terms of maximum temperatures. (ASTM E 119)

2. The test should give graduated results instead of go/

no go

3. The test must be simple to operate and not depend upon

judgment of the operator.

4. The test must give reproducible results with precision

within + 10 percent.

5. The test results should be available within a short

period of time.

6. The initial cost of the apparatus and the operating

costs should not be excessive.

3
A series of developmental tests and trials led to the

formulation of apparatus details, the selection and preparation

of specimens, and a suitable test procedure. The apparatus and

test procedure described in the following sections were used

in this study and are written in a form which may be suitable

as a proposed test method.

3. TEST APPARATUS

Figures 1 and 2 are photographs of the test apparatus.

Figure 1 shows the basic apparatus. Note that an asbestos

board shield has been provided to protect the vertical fuel

line from excessive heat during extended periods of operation.

Figure 2 shows the specimen in test position and accompanying

instrumentation. Schematic drawings are presented in plan and

elevation as figures 3 and 4. A materials list giving dimensions and numbers corresponding to the item shown in the

drawings is given in table 1. The apparatus was designed

and constructed with as many commonly available standard components as possible to keep costs at a minimum.

Table 1. List of Materials

1. Base Plate - 1/4" Brass - 6 inches by 18 inches

2. Gage and Support Angles - 1/8" Brass

3. Mixing Chamber - Nominal 1-1/2" x 1/2" Copper

Reducer (1)

4. Line Valves - 3/8" Laboratory Stop Valve. Lever

Handles have been rebored to 9/32" Orifice (2)

5. 1/2" X 3/8" Copper Reducers (2)

6. 3/8" I.D. Rigid Copper Tube. Type "L"

7. 3/8" X 90" Copper Elbows (6)

8. 3/8" X 2" Wing-Tip Burner with .040 inch Opening

(2)

9. Sample Holder

Base - 1/2" brass rod

Swivel rack - 1/4" brass rod

10. 1/2" Threaded Disconnect

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Natural city gas (95% methane) and compressed atmospheric

air are mixed thru a "Y" connection just ahead of the threaded

disconnect. The air-fuel mixture moves into a mixing chamber

that also acts as a constant pressure plenum. From this point

the fuel mixture passes through two control level valves and

is distributed to the wing-tip burners. The control level

valves are used to adjust fuel between the upper and lower

burners and to keep the impingement of the flames on the top

and bottom surfaces equal. Although these 3/8-inch stopcocks

are a common laboratory plumbing item, the orifice of each was

enlarged to 9/32 inch diameter to increase the volume of fuel

at the burner tips. The wing-tip burner opening width is .04 0

in, a critical measurement.

It is necessary to use different size sleeves that fit

over the upper arm of the specimen holder to keep different

thicknesses of board in a level plane. Thin shims may

occasionally be required for severe variations in board thickness (commonly referred to as caliper)

4. TEST SPECIMENS

Each specimen was 2 + 1/16 in (5.08 cm) by 16 + 1/16 in

(40.64 cm) cut from the long or machine direction of the

board. The specimens were saw cut rather than scored and

snapped to insure close tolerances. Care was exercised in

the selection of the specimens to be tested in order to

achieve a reasonably good representative sampling. For instance,

the specimens were neither cut from the "stream merging points"

that occur approximately one-third in from either edge, nor

cut any closer than 8 inches in from either edge as many

manufacturers may use a "hard edge" formula mix. By following

these guidelines the area was avoided where most gypsum boards

are reduced in caliper in order to form an exposed, featured,

or tapered edge to receive a joint finishing treatment.

Each specimen was conditioned for a period of 24 hours

in a 68 + 5°F (20 + 2.5**C) conditioning room or chamber with

a constant 50+5 percent relative humidity (RH) . A 9/64

inch hole was drilled through the core one inch from one end

of each specimen to accommodate a clip from which a weight was

suspended.

At least six specimens were prepared of which four were

randomly selected and tested to obtain an average time to

failure. The following information about each specimen was

recorded

9
Manufacturer's name

Product designation

Plant where produced

Production code number

Caliper (thickness) (mm)

Specimen size (cm)

Specimen weight (grams)

Test results (time to

failure) (min:sec)

Deflection failure (D) Break (B)

5. TEST PROCEDURE

The test was started by igniting the air-fuel mixture.

The mixture consisted of city gas and air with flow rate of

3 0.4 0 and about 1.0 ft /min, respectively. An 8 inch probe with

a 20 gage chromel-alumel thermocouple attached was then positioned into the specimen holder. Eight temperature points at

3/8-inch intervals were then recorded axially, four across the

centerline of the flame and two above and two below at midpoints

(see fig. 5)?. An average flame temperature of 1,780 + 25 °F

(971 + 14°C) (see fig. 6) was achieved. Necessary adjustments

in the air-fuel flow rate and control valves were made to stabilize the temperature reading. The thermocouple probe was

then removed.

The conditioned specimen was then inserted securely in

the specimen holder face up at a 90"* angle to the plane of the

burners. The weight suspension clip was fastened to the end

of the specimen and the proper weight attached, depending on

the thickness of test specimen:

Thickness of Specimen Weight

3/8 in

1/2 in

5/8 in

(9,57 mm)

(12.7 mm)

(15. 9 mm)

112.5 grams

150.0 grams

187.5 grams
AXIAL POINTS FOR

TEMPERATURE MEASURMENTS

Figure 5. Axial Points for Temperature Measurements

11
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12
The specimen was swiveled into the plane of flames and

stop watch was started simultaneously. The reading on the face

edge of the deflection scale was noted within the first 15

seconds. Time to failure was determined when the specimen broke

or deflected on the scale numerically equal to three times the

thickness of the test specimen on the leading edge of the

deflection scale.

It was found desirable to run several preliminary specimens

prior to the formal test in order to bracket failure time or

gain experience with new materials. A minimum of four specimens of each material were tested and the failure time was

recorded as an average of these four tests.

6. CALIBRATION OF APPARATUS

An initial series of thirty tests was conducted with

1/2 inch (12.7 mm) Type X and 1/2 inch (12,7 mm) regular

gypsum wallboard to determine the weight factor for the

cantilevered end. The primary purpose of the weight is to

accelerate the test. Once the 150 gram weight proved satisfactory for 1/2 inch material, the other weights were established in direct proportion to the thickness being tested.

Concurrent calibration of the test apparatus included

detailed measurements of the air and gas flow rates and

flame temperature profiles, (see fig. 6) Calibrated flowmeters were used to establish the flow rates for the air and

fuel in SCFH.

Due to the importance of the thermal exposure, extensive

measurements were taken of the flame temperature. A two

channel recorder was used. Temperature profiles were recorded

with two different size chromel-alumel thermocouples? one, a

very sensitive 36 gage, and the other, a slower response 20 gage.

Measurements were made throughout the luminous region of the

flames without a sample present. Eight points were used to

determine an average flame temperature. The locations for

these points are detailed isometrically in figure 5.

The 1,780 + 25°F (971 + 14''C) effective flame temperature

has been established as the optimum operating range for the

apparatus. The impinging flames were determined to be borderline turbulent thru calculation of the Reynolds number [6]

13
7. DISCUSSION OF RESULTS WITH PRESENT APPARATUS

In order to achieve an industry wide fire endurance rating,

six different manufacturers' products are normally used in

the construction of the test wall or ceiling membrane for

each industry sponsored ASTM E-119 test. Sample materials

from six different manufacturers with the identical production

coding as that which had been used sucessfully to achieve

one and two hour endurance ratings were acquired from a

testing laboratory to correlate this test method with the

ASTM E-119. The results of a formal series of tests are

presented in the Data Sections (8.1., 8.2. and 8.3.).

The data^ are also plotted on the charts shown as

figures 7 and 8 along with results accumulated during the

development and calibration of the test. Additional materials,

both regular and Type X, were purchased from local suppliers

to compare products from different plants available on the

open market. In addition, laboratory formulations were

prepared having varying additives to access the sensitivity

of the instrument and were ranked correctly. The letter designation in figures 7 and 8 correspond to the code letters for

materials listed in the tables (section 8)

A summary of these data offers several conclusions as to

the validity of this test method. Analysis of data shows that

the average coefficient of variation for a single test of one

type of material from a given manufacturer is + 8%. Further,

the identification of an "intermediate" formula which allows

for the addition of small quantities of glass fiber into the

regular formula for strength can be screened by this method

where other tests have indicated such formulas would qualify

as Type X.

There are essentially four classifications of gypsum wallboards that can be determined by this test method as follows:

1. Regular gypsum wallboard - Regular core formula

as manufactured to ASTM C-36 Standard Specifications.

2f Intermediate formulations ~ Regular with small

quantities of glass fiber or gypsum boards with

insufficient fiber content (probably less than

4 pounds per MSF) or short lengths of glass

fibers (less and 3/8 inch) to qualify as Type X.

3. Type X - Manufactured in accordance with ASTM C-36

Standard Specifications for extra fire resistance.

Each point in the figures is based on the mean of at least 4

tests of each specimen.

14
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4. Improved Formula Type X - Meets the ASTM requirements for Type X, but contains additional quantities of glass fiber and/or other additives to

improve the performance.

Over 400 tests have been conducted during the development

and refinement of this test procedure. In addition, the

apparatus has been in operation continually for more than

six hours on two occasions to determine its serviceability.

17
, . r; ,

, . DATA SECTION

8.1. Test Results of 1/2" Type X and Improved Formula Type X

Specimen Specimen Wt. Time to Failure Average Time

Source Number Thickness (grams) min : sec to Failure

J. 1 1/2" 199 3:46

2 1/2" 194 3:49

3 1/2 195 3:45

4 1/2 194 3:45 3:46

G. 1 1/2" 203 4:44

2 1/2" 202 4:34

3

T / II 1/2 204 4:41

4

T / n II 1/2 206 4:34 4:38

M. 1 1/2" 202 4:14

2 1/2" 202 4:16

3 1/2" 205 ^ 4:10

4 1/2" 205 4 : 12 4 : 13

F. 1 1/2" 192 3:38

2 1/2" 184 3:34

3 1/2" 185 3 : 39

4 1/2" 186 3 : 37 3 :37

J. 1 1/2" 219 3:57

2 1/2" 217 3:55

3 1/2" 215 4:01

4 1/2" 218 3:56 3:57

M. 1 1/2" 202 4:21

2 1/2" 208 4:25

3 1/2" 207 4:26

4 1/2" 207 4:26 4 :27

0. 1 1/2" 196 4:05

2 1/2" 194 4:00

3 1/2" 191 4:04

4 1/2" 190 4 : 07 4:04

S. 1 1/2" 208 4:42

2 1/2" 212 . 4:47

3 1/2" 207 4:35

4 1/2 " 216 4 : 48 4:43

s1 1/2 215 4:49

2 1/2" 213 4:47

3 1/2" 209 4:45

4 1/2" 213 4:47 4:47

F. 1 1/2 " 186 4:03

2 1/2" 184 3:56

3 1/2" 182 3:59

4 1/2" 184 3:57 3:59

18
8.2. Test Results of 5/8" Type X and Improved Formula Type X

SiDec imen 5?DPciinen Wt Time to Pai 1 urt^ avp>Tacrp Timp

Source Number Thickness (gramsmin : sec to Failure

S. 1 5/8" 256 4:43

2 5/8" 250 4:22

3 5/8" 251 4 : 45

4 5/8" 246 4:49 4:39

G. 1 5/8" 243 7:39

2 5/8" 244 7:51

J

4 5/8" 251 7:58 7:46

F. 1 5/8" 252 5:57

2 5/8" 245 5:38

3 5/8" 245

4 5/8" 244 5:37 5:41

F. 1 5/8" 243 5:38

2 5/8" 243 5:47

3 5/8" 242 5:50

4 5/8" 244 5:44 5:45

0. 1 5/8" 257 6:37

2 5/8" 253 6:05

3 5/8" 250

4 5/8" 251 6:13 6:17

S. 1 5/8" 250 4:26

2 5/8" 245 4:31

3 5/8" •* ^ 4 5/8" 249 4:52 4:38

J. 1 5/8" 237 5:08

2 5/8" 236 5:07

3 5/8" ^ ^ o 4 5/8" 242 4:49 5:02

J. 1 5/8" 261 4:47

2 5/8" 261 4:50

3 5/8" ? R7 4 • 4 4 5/8" 257 4:22 4:41

M. 1 5/8" 248 5:24

2 5/8" 240 5:12

3 5/8" 242 5:29

4 5/8" 241 5:40 5:26

M. 1 5/8" 244 5:36

2 5/8" 242 5:27

3 5/8" 241 5:38

4 5/8" 244 5:36 5:34

19
8.3. Test Results of 1/2" and 5/8" Regular Formula

Specimen Specimen Wt. Time to Failure Average Time

Source Number Thickness (grams) min:sec to Failure

S1 1/2" 181 0: 29

2 1/2" 184 0: 33

3 1/2" 182 0:30

4 1/2" 190 0:39 0:33

0. 1 1/2" 184 0 : 31

2 1/2 180 0:30

3 1/2" 183 0:33

4 1/2" 186 0:35 0:32

G. 1

1 / O II 1/2 193 0:35

2

T / 1 II 1/2 195 0:44

3 1/2" 194 0:48

4 1/2" 190 0:41 0:42

S1

1 / '^ II 1/2 187 0 : 49

2

1 / II 1/2 184 • 0 : 36

3 1/2" 188 0:51

4 1/2" 189 0:46 0:45

0. 1 1/2" 181 0:37

2 1/2" 181 0 : 41

3 1/2" 183 0:34

4 1/2" 180 0:35 0.37

G. 1 1/2" 193 0:49

2 1/2" 190 0:44

3 1/2" 194 0:44

4 1/2" 193 0:47 0:46

G. 1 5/8" 246 0:59

2 5/8" 248 1:06

3 5/8" 244 1:37

4 5/8" 243 1:43 1:21

G. 1 5/8" 243 1:27

2 5/8" 244 1 : 34

3 5/8" 248 1:38

4 5/8" 244 1:17 1:29

M. 1

c / rt II 5/8 214 1 : 09

2

c y o If 5/8 215 0 : 58

5/8 1:00

4 5/8" 212 1:03 1:03

0. 1 5/8" 230 1:08

2 5/8" 222 1:12

3 5/8" 226 1:05

4 5/8" 228 1:10 1:09

20
9. CONCLUSIONS

The bench test for Type X core described in this report

has been judged suitable based on the results of tests during

its early stages of development. Not only will it distinguish

between variations in core formulations, but it is sensitive

to different concentrations of glass fiber as well as fiber

length. The test seems unaffected by variations within nominal

manufacturing tolerances in caliper, weight and density. The

test method clearly satisfies each of the initial goals set for

its development. Correlation is evident between this test

method and ASTM E-119 in the thermal levels, flexural stressing

and identification of those materials that are identical in

performance to those that have performed satisfactorily in the

full-scale tests..

Although designed essentially as a quality control test,

the test procedure also has merit as a research tool for the

evaluation of changes in core formulations.

10. RECOMMENDATIONS FOR FUTURE WORK

Improvements of a convenience nature may be introduced and

research with other fuel sources such as propane or oxyacetylene may refine the operation of this apparatus. It may also

be useful to investigate the effect of the many different surface finish materials that utilize gypsum wallboard as a substrate.

Although the test apparatus appears to work as intended in

its present state of development, the proof will lie in the

fabrication of duplicate equipment and achieving the same

results. It is, therefore, desirable that other laboratories

reproduce the apparatus in order to evaluate results through

inter laboratory round-robin testing.

21
APPENDIX A. THERMAL VALUES OF GYPSUM

The following data are recommended for use in calculating

the heat transmission coefficients or "U" values for gypsum

wallboard products used in construction systems:

Thermal Conductivity Values

Thickness Conductance "C"

Btu/ft^ sec

Resistance "R"

2 Btu/ft sec

3/8" (9.525 mm) 3.00 0.33

1/2" (12.7 mm) 2.36 0.42

5/8" (15.9 mm) v 1.88 0.53

1" (25.4 mm) 1.20 0.85

APPENDIX B. SI CONVERSION FACTORS

The conversion factors listed in this appendix may be

used to convert the U.S. customary units to the International

System of Metric Units (SI) . For further assistance refer to

ASTM E-380 or the ASTM Standard Metric Practice Guide. The

conversion factors are as follows:

1 inch = 2.54 cm (25.4 mm)

1 foot = 0 . 305 m

eB°F = 20°C ,

• 212°F = 100°C

800°F = 427'»C

1,780*'F = 971°C

1 Btu/(ft^ sec) =1.14 W/cm^

22
REFERENCES

[1] U.S. Bureau of Mines, Mineral Industry Survey, 1972 and

through 2nd quarter 1973.

[2] Annual Book of ASTM Standards, Part 14, American Society

of Testing and Materials, Philadelphia, Pa., 568-586 (1973).

[3] Annual Book of ASTM Standards, Part 9, American Society

of Testing and Materials, Philadelphia, Pa., 31-32 (1973).

[4] Abbey, C. E. , Type X Wallboard, What It Is and Where and

When It Originated, Southern Building Magazine (Apr. 1966).

[5] Annual Book of ASTM Standards, Part 9, American Society

of Testing and Materials, Philadelphia, Pa., 347-352 (1973).

[6] Kreith, F. , Principles of Heat Transfer, International

Textbook Co., 331-344 and 366-379 (1968).

23
NB<-114A (MLv. V. /ji " U.S. PEPT. Of COMM. 1. pilHI.K A riON OK Ulil'OKT NU. BIBLIOGRAPHIC DATA

sneET NBSIR r2. Gov't Accession

No.

3. Recipient's Accessiun Nu.

i. TlW.l. AND SDin i l l.l-. Development of a Bench Test For Type X Core Gypsum

Board \

6. Performing Organization Code

7. AU rilOR(S)

J. L. Houser

8. Performing Organ. Report No.

9. F'ERI-ORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

lU. rroject/ 1 ask/ Work Unit No. 4906571

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

same as No. 9 \

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-worcl or less (actual summary of most si^ilicant inlormatiott. If document includes a significant

bibliography or literature survey, mention it here.)

This Daoer describes the develooment of a test method for

determining that the core material in a gypsum board sample qualifies

as Type X. A 2 inch (5.08 cm) by 16 inch (40.64 cm) specimen is

flexurally stressed during the test by suspending a weight from the

cantilevered end of the test sample. The specimen is swiveled into

the center of a two burner turbulent flame at an average temperature

of 1,780°F (971*C) . The burners are positioned from above and below.

The test is terminated when the specimen either breaks or deflects

through an arc three times the specimen thickness. Results show this

method to be repeatable with a coefficient of variation equal to + 8

percent for a given type of material from a single manufacturer.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by se/nico/ons; Building codes; construction materials J fire endurance ratings; fire tests,** gypsum.

18. AVAILABILITY E Unlimited

1

' For Official Distribution. Do Not Release to NTIS

[_ ' Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. CH

1 ! Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

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21. NO. OF PAGES

22

20. SECURITY CLASS

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22. Price

USCOMM-DC i;yO/S2-P7.